Remote control system for radioreceivers



Nov. 19, 1935. A. A. THOMAS REMOTE CONTROL SYSTEM FOR RADIORECEIVERS Filed Feb. 8, 1950 9 Sheets-Sheet l Nov. 19, 1935. A. A. THOMAS 2,021,705

I REMOTE CONTROL SYSTEM FOR RADIORECEIVERS Filed Feb. 8, 1930 9 Sheets-Sheet 2 J Nov. 19, 1935. A. A. THOMAS 2,021,705 l REMOTE CONTROL SYSTEM FOR RADIORECEIVERS Filed Feb. 8, 1930 9 Sheets-Sheet 5 !lllllllllllillllllll!'5 1F5 l l. I ll 1 l IIIIIIIIIVIII i Nov. 19, 1935. A. A. THOMAS 2,021,705

REMOTE CONTROL SYSTEM FOR RADIORECEIVERS Filed Feb. 8, 1950 9 Sheets-Sheet 4 INVENTOR "Nov. 19,1935. \A. A. THOMAS 2,021,705

REMOTE CONTROL SYSTEM FOR RADIOREGEIVERS Filed Feb. 8, 1930 9 Sheets-Sheet 5 INVENTOR Nov. 19, 1935. A. A. THOMAS REMOTE CONTROL SYSTEM FOR RADIORECEIVERS .R T0 t 2 3 INVENTOR Nov. 19, 1935.

A. A. THOMAS 2,021,705

REMOTE CONTROL SYS TEM FOR RADIORBCEIVERS Filed Feb, 8, 1930 9 Sheets-Sheet INVENTOR Nov. 19, 1935. A. A. THOMAS 2 RENOTE CONTROL SYSTEMF OR RADIORECEIVER Filed Feb. 8, 1950 9 Sheets-Sheet a INVENTOR Nov. 19, 1935. A. A. THOMAS REMOTE CONTROL SYSTEM FOR RADIORECEIVERS Filed Feb. 8, 1930 9 Sheets-Sheet 9 mmmp Patented a N... 19, 1935 UNITED STATES PATENT OFFICE REMOTE CONTROL SYSTEM FOR RADIORECEIVERS 22 Claims.

My invention relates to the art of controlling radio receivers from a distance, and its object is to provide an electric control system of novel construction and operation for tuning in any desired station from different rooms in a house. In accordance with this invention, a tuning box or panel is placed in each room where the receiver is to be operated, and each room has its own loudspeaker connected with the control box. These individual tuning devices may be in the form of a small portable box that can be put anywhere, or they may be built into the wall so that only the front plate or panel shows. Each control box has a set of tuning keys or push buttons representing certain selected stations, a volume knob for regulating the associated loudspeaker, and an on-oif switch for 'the electric power supply.

The individual control units in my remote tuning system are connected not only with the radio receiver but with each other in such a way that the operation of any unit is automatically signalled to all the others. When a person pushes a button on his control box to bring in a certain station, a light flashes on all the control panels in the house as a signal that somebody is tuning the receiver. As soon as thedesired station is in, a window identifying that station automatically lights on every control box. Whoever wants to hear that particular station need only close the main switch on his panel, and the loudspeaker in the room brings in the broadcast reception.

In a preferred embodiment of my invention, the station selecting switches in the control boxes are operated by keys or buttons which need only be pushed in for a moment. That is, after the operator presses the desired button as far as it will go, he can remove his finger and the button stays in. When a tuning button on any panel is pushed in, the buttons on all other panels are automatically locked against operation, including the unused buttons on the selecting panel. This assures the tuning of the receiver from any panel without interference by attempted operation of anothercontrol box. Each panel has a special key or button for releasing the tuning keys of all panels, so that the occupant of each room containing a panel has full control of the receiver. The release of the buttons is accompanied by the extinguishing of the signal light. In; other words, when a person looks at his control panel and sees no light on it, he knows that nobody is using the radio receiver.

In the broad aspect of my invention, any practical mechanism may be employed'to move the tuning shaft of the receiver to correct position when a remote control button is pushed in. One form of tuning mechanism devised by me comprises a series of disks mounted on the tuning shaft for controlling a set of switches, which in turn control the circuit of an electric motor connected to the shaft. The arrangement is such that, when a tuning button is pushed in, the particular disk representing the selected station automatically opens the motor circuit and stops the shaft in tuning position. To enable a person to go on a dialing expedition for any suitable program, I provide a separate button which holds the motor circuit closed as long as the button is pushed in. When the operator gets what he likes through the loudspeaker, he simply releases the button and the station remains in tune. The rotation of the tuning shaft in the receiver is automatically reversed at each end of the scale, so that a person using the remote control does not have to bother about which way the shaft will turn.

The various features of novelty and practical advantages of my multiple tuning system will be 5 understood from a description of the accompanying drawings, in which Fig. 1 illustrates diagrammatically a radio receiver operatively connected to several remote control panels located in different rooms in a house;

Fig. 2 shows a sectional plan of the interior of a remote control box embodying certain features of my invention, this view being a section on line 2 2 of Fig. 3;

Fig. 3 represents a transverse section through the control box on line 3-3 of Fig. 2;

Fig. 4 is an enlarged fragmentary view on section line 4-4 of Fig. 3, to show the mounting-of certain switch units in a common insulating base;

Fig. 5 is a detached perspective of one of the switch units operated by push buttons on the control box;

Fig. 6 shows a longitudinal section of the control box on line 6-6 of Fig. 3, except that the central portion of the box is broken away for lack of space;

Figs. 7 and 8 are fragmentary detail views on lines 1-1 and 8-8 of Fig. 2, respectively, to show the switches controlled by the release key and by the special key that brings in any station, these switches being shown in normal open position;

Fig. 8a is like Fig. 8, with the key partly pushed in to close one of the associated switches;

Fig.9showsaplanviewofthetuningshaftin the radio receiver and the associated control mechanism;

Fig. is a side view on line IOHI of Fig. 9, showing one of the control disks on the tuning shaft and the associated switches, the latter being in normal position;

Fig. 11 is like Fig. 10, but showing the condition of the switches when the associated disk is in tuning position for the selected station;

Figs. 12, 13, and 14 (on sheet 3) show various views of an automatic reversing switch for the electric motor that drives the tuning shaft, Fig. 14 being a section on line M-ll of Fig. 12;

Figs. 15 and 15a together constitute a diagram of circuit connections between the radio receiver and the remote control units;

Fig. 16 is a circuit diagram of electrical connections between the radio receiver and the loudspeakers of the control units;

Fig. 17 is a diagram of circuit connections for the reversing switch shown in Figs. 12-14;

Fig. 18 represents an enlarged fragmentary view on section line i8-l8 oi Fig. 2 to show one form of main switch that may be used in each control box;

Fig. 19 shows a perspective of a control box or cabinet which also contains the loudspeaker;

Fig. 20 illustrates a control box and loudspeaker mounted separately in the wall of a room;

Fig. 21 shows a control box and loudspeaker mounted in the wall as a unitary structure;

Fig. 22 is a circuit diagram of a modified control system in relation to the universal tuning key; and

Fig. 23 shows a form of mounting for the universal tuning key and associated switches employed in the system of Fig. 22.

I shall first describe the general operation of my multiple-unit remote-control system as diagrammatically represented in Fig. 1. A radio receiver R of suitable construction is operatively connected by an electric cable 10 to all the remote control units Q in the house. For the purpose of explanation, I have considered it sumcient to show three control units Q located in three rooms I, II and III, but any number of units may be employed. Each room also hasa loudspeaker S oneratively connected to the associated tuning device by conductors II. If the loudspeaker S is of the table type adapted to be placed in any part of the room, the conductors I! may be in the form of an electric cable adapted to be plugged into the front panel of the tuning device, as indicated at l 3. The loudspeaker 8 connected with each tuning device may be of any approved t pe, structure and design. At the present time, the most popular loudspeaker is the moving coil type. Instead of using a loudspeaker separate from the control unit, I may combine the two into a unitary structure, as I shall explain later.

The remote control units Q may be constructed in the form of small boxes that can be placed in any convenient location in the room, or they may be built permanently into the wall as indicatedln Fig. 1. The structural details of the control units Q will presently be described, and at this point I shall refer only to the general operation of these units. I have assumed that each unit is capable of tuning in ten selected stations, and so the front panel of eachunit is provided with ten tuning keys or push buttons II, which may conveniently be arranged in two rows of live each. The ten stations represented by these buttons are indicated in Fig. 1 by the reference letters A to K. Opposite each tuning key or buticon is a window I5 which may carry the call letters or other identifying marks of the particular station represented by the adjacent key. Each 5 control panel also has an on-oiI switch Ii, a volume control knob H, a universal timing key II,

a release key l9, and a pair of signal lamps 2| and 21. I might explain here that, in referring to the parts ll, l8, and I8 as keys or buttons. I 10 use these terms in the broadest possible sense, both in the description and claims, to include any practical form and structure of movable flnger piece for operating the necessary switches.

Let us suppose that the occupant of room 116 wants to tune in station C. All he has to do is to throw on the main switch I6 and then press the button opposite window C. The button need not be held in, but may be released after it has been pushed in as far as it will go. The depressed 20 button remains locked in actuated position, and at the same time all the other tuning buttons on the panel are held against operation. When the main switch I6 is closed, the lamp 2| automatically lights to indicate that the power is on. This 25 lamp may shine through a suitably colored lens-= say, a bright green. When the tuning key for station C is pushed in, the lamp 2B automatically lights and it may shine through a differently colored lens, such as red. For convenience of :0 description, I shall refer to the lamp 20 as the' red signal and to lamp 2| as the green signal, without thereby intending any limitation as to colors. When the desired station is timed in, the window C opposite the actuated key automati- 25 cally lights and stays lighted as long as that particular station remains in tune. This enables the operator to observe at any time which station is sending the broadcast reception. To shut of! the radio receiver, it is only necessary to open the 40 main switch [6, which opens all circuits and ex-- tinguishes all lights on the control panel.

Thekey IBisusedwhenitis desiredtotunein a station not represented by the automatic tam-- ing buttons H. The pressing of key II causes (.3 the tuning shaft of the receiver to turn slowly" from one end of the dial to the other, and as each broadcasting station crosses its tuning position, the occupant of the room hears the program through the loudspeaker. When he gets the kind of program that he likes, he simply releases the key I! and the station remains in tune. Since the key or button [8' enables the operator to go on a station-fishing or dialing expedition, as it were, I may appropriately call it the dialing key. volume of the loudspeaker is controlled by tuming the knob I! one way or the other. By pressing the button 19, the operator unlocks all the tuning keys and releases the key that was previously actuated.

When any control unit Q is operated, that fact K is automatically signalled to all the other units in the house. For example, when the occupant oiroom I presses any one of the tuning buttons I4 and IS, the red signal 20 instantly lights on all panels. This warns everybody that someone inthe house is operating his remotecontrol. Let as assume that the occupant of room I has pressed the button for station C. As soon as that station is in tune, the corresponding windows in all control panels are automatically lighted, so' that the occupants of the difierent rooms can tell which station has been tuned in by simply looking at their respective panels. If," let us say, a person in room III feels like getting [6 Thethe broadcast of station C that was tuned in from some other room, he simply closes the main switch 16-, whereupon the associated loudspeaker S is automatically connected with the radio receiver.

I have said that, when a tuning key l4 on any panel is operated, all the other tuning keys on that panel are locked against manipulation. This automatic locking of the keys extends to all the other control panels. Consequently, when,

the occupant of a room sees the red Hana] 20 flash up, he is not only warned that somebody in the house is tuning the radio receiver, but he is actually prevented from operating. his own tuning keys, so as not to interfere with the tuning of the receiver. It is, of course, necessary to release the locked keys before they can be used to tune in a station, and I prefer to control this releasing operation from each panel. Suppose the occupant of room II, after getting the red warning signal 29, finds that he gets no reception through the loudspeaker on closing the main switch I6; this may mean that the station originally tuned in by somebody else has gone the air. It the occupant of room II now tries to bring in his own station, he finds that the'buttons l4 and 13 are locked. He therefore presses key I! which instantly releases all the tuning keys on his panel, so that he can bring in any station he wants. Although the releasing key I! on each panel gives the occupant of each room the power to place his control device in operative condition, even if somebody else has already tuned the receiver, 1. is to be expected that the members of a household will respect each others tuning rights when the red signals 20 flash on.

The main purpose of locking the control panels when a tuning button on any'panel is pushed in, is to prevent the accidental or unintentional operation of a second panel. For instance, a child in the room might be attracted to the panel when the red light 20 goes on and try to push one of the tuning buttons. Or, it might happen that the red signal lamp 20 had burned out, so that the persons in the room would not be informed of the radio set being tuned from some other panel. The inoperative condition of a signal lamp will not affect the au'omatic locking of the tuning keys on all panels by the operation of any key on any panel. In other words, when a person pushes in a key, he is assured that his tuning operation will not be disturbed in another room Figs. 2-8a and .Fig. 18 show the construction of a tuning unit Q, and since these are supposed to be duplicates of each other, a detailed description of one unit includes them all. The operative parts of each control unit are housed in a suitable box or casing indicated as a whole by W and comprising a bottom or. base plate 22, sides 23, top and bottom pieces 24 and 25, a pair of inside partitions 26 and 21. and a removable cover 26. The parts 22, 23, 26, and 21 may be cast or molded as a single piece of insulating material, such as bakelite, fiber, porcelain and the like. The end members 24 and 25 in some instances may be formed integral with the body of the box, but it is usually better to make them separate so that they can be removably attached to the sides 23 by screws 29 or otherwise (see Fig. 2) This .iacilitates assembling of the inside mechanism, as will presently be better understood. The cover 23, which is of suitable color and design, is removably fastened to the box by screws 30, which in this instance enter the lateral extensions or shelves 3i projecting inwardly from.

the longitudinal partitions 24 and 21, as best shownin Fig. 3. The shelves 3| may be formed integral with the partitions from which they project. I! the box W is to be mounted in the wall on; room, the sides 2: are provided with 5' lateral flanges 32 adapted to receive screws or other fastening members 33 which enter the supporting wall 34. If desired, the top and bottom pieces 24 and 26 of the box may also have securing flanges 32, as shown in Fig. 6, although that is not absolutely necessary. Any other practical means may be employed for properly mounting the remote control boxes permanently in the walls of the different rooms. If these boxes are intended to be portable, the flanges 32 are not necessary, and the box will be so designed that it can be placed anywhere in the room for convenient operation.

In the center of box W is a block 36, which may conveniently be formed integral with the bottom plate 22. The block 36 has a series of cross-slots 36 equi-distantlyspaced. In the present embodlment of my invention there are five slots 36. because ithas been assumed that the tuning keys l4 are arranged in two rows of five each, and the slots 36 are in lateral alignment with the keys, as will be clear from Fig. 2. In each slot 36 of block 35 is mounted a rectangular insulating piece 31 which carries two sets of flve switch arms marked 33, 39, 40, 4|, and 42. These switch arms may be in the form oi! flat spring blades of good conducting metal and are fitted at their inner ends in slots 43 in the supporting piece 31. An insulating pin 44 or the like may be used to secure each set of switch blades in position. A longitudinal rod or bolt 46 passing through block .36 holds the insulating pieces 31 firmly in slots 36. Any other practical mounting of the switch members 38-42 may be used, but the construc tion just described has the advantage or easy assembly. In the first place, the individual switch arms are mounted on the fiat pieces 31 and the latter are then inserted into slots 36 in a tight fit. The rod or bolt is then passed through block 35 and members 31, whereby all the switches 45 are properly and securely positioned. As best shown in Figs. 3 and 6, the switch arms 39 and 40 are connected by an insulating stud or washer 46, which may be attached to either of those arms, and a similar stud 41 connects the switch 5 arms 4| and 42. The bottom plate 22 of the control box carries a pair of contact bars 46 arranged in alignment with the free ends of switch arms 42, as best shown in Fig. 3.

The automatic tuning keys or buttons H are slidably mounted in the lateral extensions or shelves 3| of partitions 26 and 21. A simple way to hold the'keys in place is by means of axial slots 43 and screws 50, as illustrated in Fig. 3. The screws 50 are removably mounted in shelves 0 3| and extend at their free ends into the key slots 49. This simple arrangement permits the necessary axial movement of the keys and yet locks the same against turning. The set-screws 50 are arranged at such an angle that they are 5 easily inserted or withdrawn by an ordinary screw-driver. The keys or push buttons i4 are preferably cast or molded of suitable insulating material such as bakelite, porcelain, celluloid, fiber, and the like. The inner end of each key rests against the free end of the associated spring arm 36, which normally holds the key in raised or projected position. It is clear from Fig. 3 that, when a key I4 is pushed in as far as it will go, the switch members 33 and 33 are closed first,

then the switch members 48 and 4| are closed. and finally the switch member 42 is moved against the adiacent contact bar 48. Of course, when a key is pushed in by a quick movement, as

is usually done, the closing of the three switches 38-88, 48- and 42-48 takes place almost simultaneously. When an actuated key is released, the five spring arms 38 to 42 instantly snap back to normal open position, and the upper switch arm 38 pushes the key out until the inner end of slot 48 strikes the projecting end of screw 58. The inward movement of each key is limited by the lower switch arm 42 engaging the fixed contact bar 48. The switch arms 88-42 may be made of spring brass, bronze, or the like, and have just enough resiliency to offer the right amount of resistance to the movement of key I4.

The inner partitions 26 and 21 of box W are provided with a pair of aligned slots 5| for slidably supporting a key-locking plate 52, which may be stamped from a sheet aluminum, bakelite, fiber, or other suitable material. The plate or slide 52 is formed with slots' or recesses 58 arranged in line with the tuning keys l4, as shown in Figs. 2, 3, and 6. Each key I4 has a pair of transverse grooves or slots 54 and 55. When the keys are in normal position, the slots 55 are in line with slide 52, as may be seen in Figs. 3 and 6. The locking plate 52 is normally held against a fixed stop or stops 56 by one or more contracting coil springs 51, which are attached at one end to the wall 25 of the box by screw-eyes 51' or otherwise. The stops 56 may be a pair of posts or studs projecting from the bottom of the box. In

.the normal position of slide 52 any one of the Fig. 6), the edges 58 of recesses 53 move into locking engagement with one of the slots 54 and 55 of each key I4. Those keys that are in normal position are locked by the edges 58 entering the slots 55. When a key is pushed in, the adjacent edge 58 of plate 52 enters slot 54 and thereby locks the key in depressed position. In other words, when the slide 52 is moved out of normal position, the tuning keys 4 are locked against operation and the key which was actuated is locked against return movement. Since the keys I4 can not turn in the supporting shelves 4| on account of the slot and screw connection 48-58, the cross-slots 54 and 55 are always in operative relation to slide 52.

The slidable keylocking plate 52 is actuated by an electromagnet comprising one or more coils 59 and an armature bar 68. The coils 58 are mounted on a suitable magnetic frame which terminates in pole pieces 6| arranged at opposite ends of armature bar 68, and this frame may be attached to the adjacent end 24 of the control box. The armature bar 68 is secured to one end of slide 52 in any practical way. In Figs. 2 and 6 I have shown the armature provided with a pair of lateral lugs 62 for receiving bolts or rivets 58. When the coils 58 are energized, the armature bar 68 is drawn to the pole pieces 6| and thereby carries the slidable plate 52 to key-locking position against the tension of springs 51. When the coils 58 are de-energized, the tensioned springs 51 pull the plate 52 back to inoperative position against stops 56.

The slidable plate 52 locks not only the auto .matic tuning keys 4, but also the dialing key I8 whichisusedfortuninginanystation. For this purpose one end of plate 52 is provided with a right-angled extension or finger 54. which pro- Jects through a slot 65 in partition 21. as shown in Fig. 2. The narrow slot 55 of key I8 (see Fig. 5

8) is normally in line with the locking extension 64. Therefore, when the slide 52 is actuated by the electromagnet 58, the finger 84 enters slot 55 and locks the key I8 in normal position. The other slot 65 in key' 8 is wider than the slots 10 54 in the automatic tuning keys I4 to permit a partial return movement of the actuated key I8 after the plate 52 has been moved to locking position. The reason for this partial return of key l8 will be understood when I explain the i6 circuit diagrams of Figs. l5-15a. The key I! controls a pair of switch members 88 and 61 mounted in an insulated block 68 carried by the end piece 25 of the control box. The switch members 66 and 61 are preferably fiat spring blades of good conducting metal inserted tightly in slots in block 68 and held in place by an insulating pin 68 or otherwise. The inner end of key l8 may have an eccentric projection 18 for engaging the spring arm 66 at or near its free 28 end. An insulating post or projection 1|, which may be integral with the bottom plate 22, carries a contact 12 arranged to be engaged by the spring arm 61 when the key I8 is fully pushed in. The fixed contact 12 also acts as a stop for the inward movement of key I8.

Fig. 8a shows the dialing key |8 locked against return movement by the locking finger 84 engaging the bottom of slot 65, but the key is free for further inward movement because of the 35 depth of slot 65. Therefore, as the key is pushed farther in, the switch arm 61 engages the fixed contact 12 to close the circuit of a small electric motor that operates the tuning shaft of the radio receiver, as will later be explained. When key 40 I8 is released, it returns only partway to normal position, as shown in Fig. 80, since the locking finger 54 is still held in slot 65. This partial return movement of key I8 is suflicient to open; the switch 61-12 so that the motor circuit is in- 45 terrupted and the tuning shaft stops.

Referring to Fig. 6, a solenoid coil 18 mounted on the bottom plate 22 has a reclprocable magnetic core 14 which terminates in (or otherwise carries) a stop pin 15. A coil spring 16 normally 50.

' the electromagnet 58 is deenergized. To release the plate 52 from looking position, it is necessary to energize the solenoid 18 and that is done by the release key I8, to which I referred in a general way in connection with Fig. 1. The inner end of key I8 (see Fig. 7) engages a switch arm 18, which may be a fiat spring blade attached to the end wall 25 of the box by screws 88 or otherwise. An insulating post 8| on base 22 carries a contact 82 arranged to be engaged by the spring arm 18 when key I8 is pushed in. The fixed contact 70 82 also acts as a stop for the inward movement of the key, which is supported in normal position by the spring arm 18. When the switch 18-82 is closed, the solenoid 18 is energized to pull the pin 15 out of contact with slide 52, which is then I free to be retracted to normal unlocking position by the tensioned springs 51.

The keys I8 and I9 are slidably mounted in bushings or bosses 89, which may be integral with the removable cover 28. The slot and screw conv nection 49-59 above described in connection with keys I4 may also be applied to keys I8 and I9, as will be clear from Figs. 7 and 8 without further description. The individual tuning keys I4 may also be mounted on cover 28, like keys I8 and I9. Since the keys I 4, I8, and I9 are not connected to their associated switch arms, it is feasible to mount all the keys on the removable cover 28.

Referring to Figs. 2 and 18,. the main switch I8 comprises an insulating cam disk 84 pivoted on a stud 85 which is supported in a bushing 89 of the side wall 28. A set-screw 81 carried by cam disk 94 engages in an annular groove 89 in stud 85 to prevent lateral shifting movement of the disk. In describing Fig. 1 I referred to the member I 8 as the main switch, but in Fig. 18 the part I6 represents a finger piece attached to cam disk 84 and projecting through a slot 89 in cover 28. A contracting coil spring 99 is attached at one end to a fixed point 9| in the box, and at the other end to a pin 92 projecting laterally from cam disk 84. The spring 99 is always under tension and holds the switch in either position. The cam disk 84 controls a pair of switches, one of which comprises members 98-94 and the other comprises members 95-98. In the present instance, these four switch members are shown as spring arms mounted on a block or projection 91 at one,

end of the bottom plate 22. The two switch members 94 and 98 may be fixed contacts instead of spring arms. The inherent set or tension of spring arms 98 and 99 is such that normally they are out of contact with the associated switch members 94 and 98. Consequently, when the finger piece I8 is in oil position, the two switches 98-94 and 95-98 are open. When the finger piece I8 is in on position, the cam disk 84 presses the spring arms 98 and 95 against the contacts 94 and 98 respectively, so that the two switches are simultaneously closed. As I shall explain later on, the switch 93-94 controls a relay for operating a main power switch to connect the radio receiver with the house-lighting mains 'or other source of electric power. The switch 95-98 controls the magnetizing current for the field magnet of the associated loudspeaker S when the latter is of the moving coil type, which requires a strong electromagnetic field.

In describing Fig. 1, I spoke of a signal lamp 29 which automatically lights when a tuning key I4 is operated. Fig. 2 shows the lamp 29 mounted on the bottom plate 22 of the control box between the electromagnetic coils 59. The circuit of this lamp is closed automatically when the slidable plate 52 is moved to key-locking position. For this purpose the armature bar 89 carries an insulating strip 98 which is provided with a contact piece 99 arranged to bridge a pair of insulated contacts I99. These contacts may be spring arms fastened to the bottom plate 22. When the slide 52 is actuated to locking position by the' energized electromagnet 59, the insulated contact piece 99 strikes the switch arms I99 and closes the circuit through signal lamp 29. The resiliency of switch arms I99 insures a firm pressure contact with bridge piece 99. When the slide 52 is returned to normal position by operating the release key l9, the switch 99-I 99 is automatically opened to extinguish the red signal 29.

Each remote control box W is divided into a. series of small compartments I9I by cross-plates I92 which are removably inserted between the outer sides 23 and inner partitions 28-21 of the box. is to insert the two side edges in grooves I98 formed in sides 28 and partitions 29-21. The outer sides 28 and inner partitions 28-21 are provided at their outer ends with shoulders I84 for supporting the windows I5 which I mentioned in the description of Fig. 1. Each row of windows I5 preferably consists of a single strip of ground 1 glass or other translucent material. when the cover 28 is attached to the box, the window strips I5 are automatically secured in place, as will be clear from Fig. 3. The cover 28 has cut-out portions I95, which may be rectangular, circular or of any other outline, and are in alignment with the small compartments I9I. Each of these compartments contains a. signal lamp I98 mounted in 29 I a socket I91, which is secured to the base plate 22. The lamps I98 are arranged opposite the station-selecting keys I4, and the circuit connections (to be subsequently described) are such that when the station selected by an actuated key is intune, 85 the lamp opposite that key automatically lights. This enables the operator to tell at a distance which station he has tuned in.

The green signal lamp 2I, which automatically lights when the power switch I8 is on, may con- 80 veniently be mounted in a compartment I98 at one end of the box. The right-hand window strip I5 may extend over lamp 2 I, but I prefer to cover that lamp with a brightly colored lens to distinguish it from the station-indicating lamps I98. The volume-control knob I! (see Figs. 2 and 6) is connected to the outer end of a rotary shaft I99 which carries a contact arm I I9 arranged to move over an insulated resistance element I I2 mounted on the bottom plate 22 of the box. The rheostat 40 I I 9-I I2 is so connected with. the associated loudspeaker as to vary the volume of reproduction when the knob I1 is turned one way or the other.

In the broad aspect of my invention. the rheostat I I9-I I2 may be connectedto the radio receiver in any practical way, but in Fig. 16 I have shown a novel method of volume-control which I shall describe later on.

The key-locking slide 52 of each control box carries at one end an insulating block or plate 59 H8 on which a contact arm H4 is mounted. A second contact arm H5 is supported on base 22 so as to be engaged by arm II4 when the slide 52 is actuated to key-locking position. The switches II4-II5 of the various control units 6 are so connected in circuit that the closing of any switch automatically energizes the electromagnets 59 of all control units, so that all tuning keys are locked when a tuning key on any panel has been operated. To avoid confusion in U the drawings, I have purposely omitted all wiring in Figs. 2, 3, and 6, and I need only say that all the wires leading into the control box are contained in a cable II8, which is supposed to connect to the main cable I9. If the control units Q are built permanently into the walls of thedifferent rooms where they are located, there is no need of having a single cable II 8 leading from each box, because the wiring 'would be concealed anyway and could be arranged in the most convenient way.

I shall now describe the tuning mechanism set in operation in the radio receiver by the remote control units Q. Referring to Figs. 9, 10, and 11,

in which some parts are shown for clearness in 15- A simple way to mount the cross-plates I92 5 exaggerated dimensions, the rotary tuning shaft H1 of the receiver has a plurality of disks H8 rigidly mounted thereon. The tuning elements controlled by shaft H1 are indicated by a con- "15 denser assembly H3, which may be regarded as representing the several gangs of variable condensers with which modern radio receivers are provided. It is not necessary that the condensers H9 are mounted directly on shaft H1, for 10 they can be mounted on one or more countershafts operatively connected with the main shaft H1. When, therefore, I refer to shaft H1 as the tuning shaft, I do not necessarily mean a shaft carrying the tuning elements, but I include any shaft operable for tuning purposes. There are as many disks H8 as there are automatic tuning buttons I4 on the remote control units Q. In the present example of my invention, there would be ten disks H8 on shaft H1, but inFig. 9 I show only three disks to avoid unnecessary duplication of parts. It will therefore be understood that each disk H8 represents a certain station, and these stations are the same as those represented by the automatic tuning keys I4 on the remote control units. The disks H8 may be stamped, molded or cast of metal or insulatingmateriai, such as aluminum, bakelite, flber, porcelain, glass and other suitable substances. g The tuning disks H8 areeach provided with a notch or recess I which cooperates with an associated switch mechanism for automatically stopping the shaft H1 in tuning position for the station represented by that particular disk. This switch mechanism comprises three insulated switches represented by three pairs of contacts I2I-I22, I23-I24, and I28-I28. The switch members I2 II 22 are mounted on a right-angled bracket I21, and the other four switch members 123-426 are attached to a block or bar I28. The parts I21 and I28 are of suitable insulating material, such as bakelite, and are rigidly connected by screws I 29 or otherwise to form a unitary support for all the switch assemblies associated with disks H8. By making the parts I21 and I28 separate, it is easy to attach the various switch members thereto. The switch member I2 I is a spring arm secured at one end to bracket I21 by one or more screws I30. The switch members I23 to I26 are spring arms attached in proper position to the insulating block I28 by screws I3I or otherwise. Any other practical mounting for the switch assembly I2I-I26 may be employed. The spring arms I2I and I23 are mechanically connected by an insulating pin I32. The free end of spring arm I23 carries an insulating pin I33, which normally holds the spring arm I28 pressed firmly against the coacting spring arm I28. The normal tendency of spring arm I is to remain out of engagement with switch member I28, as 0' shown in Fig. 11. The switch arm I2I carries a projection I34 adapted to enter the notch I20 of the associated disk I I8 when the arm is pressed down. The notch I20 and projection I34 are preferably bevelled or tapered to provide a close 65' fit between them so that the disk I I8 always stops in exact tuning position.

The notches I20 of disks H8 are in such radial position that each disk tunes in a predetermined station when the projection I34 of the associated arm enters the notch of the disk. After each disk has been adjusted to correct radial position, it is secured to shaft H1 in any practical way, as by a set screw H1 passing through the hub H8 of thedisk. Aneasywaytoseteachdiskisto 18' mount it loose on shaft H1 and hold the projecthe screw H1 or otherwise. This also makes it 8 a simple matter for the owner of the receiver to readjust any disk for any other station. Manifestly, a change of that kind'requires that the call letters or other insignia of the new station be placed on the proper window of each remote 10 control panel. As a rule, however, the disks H8 will not have to be adjusted after the set leaves the manufacturer.

The resilient switch arms I2I are individually controlled by a series of electromagnets I38, 18 which are shown in the form of solenoids having each a magnetic plunger I88 connected to one end of a bellcrank I31 pivoted on a rod I38. The electromagnetic coils may conveniently be supported on a common insulating bar I38 which 80 carries a pair of brackets I48 for supporting the rod I88. The bellcranks I81,. which may be stamped from sheet aluminum, are held against axial movement on rod I38 by spaced collars I or otherwise. The free end of each bellcrank 88 I31 carries a cross-pin or lateral projection I42 arranged normally to rest on the free end of the adjacent switch arm 'I2I, as illustrated in Fig. 10. The inherent tension of spring arm I2I normally holds the bellcrank I31 in raised position, so that the connected solenoid core I38 is partly withdrawn from coil I38. In the normal position of spring arm I2I, the tip of projection I34 just misses the periphery of disk H8 or touches it very lightly without engaging the sides oi notch 35 I20. When the coil is'energized, the core I34 is pulled in and the bellcrank I81 is rocked to position I81, so that the free end of spring arm I2I is bent down as roughly indicated by the dotted outline I2I' in Fig. 10. .This flexing of 80 spring arm I2I presses the projection I 34 against the periphery of the disk H3, but the switch I2II22 remains open and switches I23-I24 and I28-I28 stay closed. The spring arms I 24 and I28 are normally so set that they bend down 88 at their free ends, as will be clear from Fig. 11. Consequently, the slight downward movement of spring arms I28 and I28 when the bellcrank I31 flexes the free end of spring arm I2l is followed up by spring arms I 24 and I28 to hold the switches closed.

The pressure of projection I84 on the periphery of disk H8 when coil I38 is energized does not interfere with the rotation of shaft H1. If desired, the periphery of disk I I8 and the tip of projection I34 may consist of (or be covered with) anti-friction material, but as a rule that will not be necessary, because the pressure between those parts can be made comparatively light. As soon as the notch I28 of the rotating disk ill comes in line with projection I34 01' the flexed switch arm Hi, the latter snaps into the position shown in Fig. 11, whereby the two switches I 23-I24 and I28I26 are opened and at the same time switch I2I-I22 is closed. The parts remain in this position as long as the circuit of coil I 38 is closed. When the coil I38 is tie-energized, the connected spring arms I2l and I28 automatically move back to normal position, carrying the bellcrank I 31 along to withdraw the solenoid core one of the remote control units Q. The function 78- of the switch assembly associated with each tuning disk II will be explained in connection with the circuit diagram of Figs. 15-15a.

Referring now to Figs. 12, 13, and 14, the tuning shaft II1 of the radio receiver is operated by a small electric motor I43. The motor shaft I44 carries a worm or spiral pinion I45 arranged in permanent mesh with a gear I46 fixed on shaft II1. The gear connection I45I46 is such that the tuning shaft II'l runs at the required low speed. The tuning dials of modern radio receivers extend through an arc of 180 degrees,

because the capacity of the tuning condensers is v adJustedfrom minimum to maximum by a half revolution of the tuning shaft. For this reason it is necessary to reverse the movement of. shaft H1 at the end of each half revolution, and this may be done either by reversing the motor shaft I44 or interposing a mechanical reversing constud I48 on which two members I49 and I50 are I with shaft II1.

mounted for independent movement. In the present instance, the member I49 is connected to pin I46 and member I50 is loose thereon. The

pivoted member I49 has two pairs of lateral extensions I 5I--I52 and I53-I54, while the other member I50 has two lateral extensions or wings I55 and I56. A contracting coil spring I51 is preferably of insulating material, carries four pairs of switch arms marked I60I60', I6II6I', I62-I62 and I63-I63'. These switch arms may simply be fiat spring blades of good conducting metal mounted at one end firmly in slots I64 of frame I41. The normal tendency of the spring arms of each pair is to remain open.

Still referring to Figs. 12, 13, and 14, the gear wheel I46 on tuning shaft II1 carries a lateral pin I65 arranged to engage the outer ends of cross-arms I55 and I56 of member I50. The two pivoted members I49 and I50 constitute a toggle adapted to operate with a sudden snap action through the tensioned coil spring I51. The rocking movements of member I50 are limited by shoulders I66 and I61 at the upper end of frame I41, as best shown in Fig. 12. When the spring I51 is to the right of pivot I46, the two toggle members I49 and I50 are in the position shown in Fig. 12, and the switches I60-I60' "and sions I5I and I53 of member I49. It is assumed in this figure that the position of pin I65 corresponds with one end of the tuning dial associated I have not considered it necessary to shown such a dial, because every radio receiver has one and its function is well understood. Let us suppose that the toggle members I49 and I50 in Fig. 12 have just been operated to close the curs when the pin I65 on gear'wheel I46 is at the end of a half revolution. The closing of those switches automatically reverses the current flow through the motor windings, so that the gear wheel I46 now turns in the direction or arrow I66.

When the pin I65 of gear wheel I46 encounters the cross-arm I56 of toggle member I50, the latter is slowly rocked counterclockwise (as viewed in Fig. 12) and carries with it the upper end of spring I51. The lower toggle member I49 remains in position to hold the switches I60I60' and I6I-I6I' closed until the axis of spring I51 crosses the pivot point I48, whereupon the tog- 5 gle member I49 is quickly snapped to the left to close the reversing switches I62-I62 and I63I63'. When that happens, the pin I65 has reached a diametrically opposite position I85 and the motor shaft I44 is reversed to rotate the gear wheel I46 in the direction of arrow I69. The operation of toggle member I49 with a snap action causes the opening of one pair of switches and the closing of the other pair of switches to take place almost simultaneously, so that the reversal of motor shaft I44 occurs at the right moment-that is, when the tuning dial is at either end of the scale. Another practical advantage of operating the reversing switch with a snap action by the toggle member 20 I49 is that the momentum of the motor shaft I44 is checked at the instant of reversal. Since the motor I43 has only a small fraction of a horsepower and takes little current. to run it,

there is no danger of burning out the motor wind- 25 ings by the instantaneous reversal of current.

The electrical connections between the motor windings and the reversing switch mechanism are diagrammatically indicated in Fig. 17. The positive and negative leads I10 and HI are supposed to be connected to the opposite sides of a direct current generator. The armature winding I12 of motor I43 is connected to the feed, wires I10 and HI through brushes I13 and commutator I14. The field winding I15 is diagrammatically represented by a pair of coils connected in series. One end of the field winding is connected by a conductor I16 to switch arms I60 and I63 in parallel, and the other end of that winding is connected by a conductor I11 to switch 40 arms I6I. and I62. The switch arms I60 and I62 are connected by branch wires I18 and I19 to the positive lead I10, and a conductor I80 connects the switch arms I6I and I63 in parallel to the negative lead "I. When the two switches I60I60 and I6I- I6I' are closed by the snap-over toggle member I49, as illustrated in Fig. 12, the magnetizing current flows through the field winding I15 in the direction of arrows IOI as follows: From positive lead I10 through 50 conductor I18, across the closed switch contacts I60'I60, conductor I16, through fl.ld winding I15 in the direction of arrows I8I, conductor I 11, closed switch contacts I6I'I6I, and through wire I80 to the return lead "I. 55 When the snap-over member I49 closes the two switches I62-I62' and I63I63, the magnetizing current is reversed through the field windings as follows: From positive lead I10 through conductor I19, across the closed switch 60 contacts I62'I62, conductor I11, through motor winding I15 in the direction of arrows I82, conductor I16, across the closed switch contacts I63-I63, and through conductor I80 to the return lead I1I. The reversal of current through 65 the shunt field winding reverses the rotation of motor shaft I 44 and tuning shaft II1.

We are now ready for the circuit diagram of Figs. 15l5a, which show the operative connections between the remote control units Q and the tuning mechanism of the radio receiver. These two figures are really two halves of a circuit diagram severed along the dash-dot line I83. This separation was necessary because it was impossible to show all the wiring on a single sheet. To avoid needless duplication of circuits I have included only five stations A-E and three control units in the circuit diagram. Any number of stations and control units may be connected in the manner illustrated in Figs. 15-15a. The tuning disks I I9, which are mounted side-by-side on shaft II1, are shown separated in face view in Fig. 15, and the dotted line 1 is supposed to indicate diagrammatically the shaft on which the disks are mounted. The automatic reversing mechanism between the electric motor I99 and the tuning shaft I I1 is indicated in Hg. 15 by the rectangular outline I99, which may represent an electric reversing switch as previously described, or mechanical reversing connections. The bellcrank connections between the switch arms I 2I and the controlling coils I95 are omitted in Fig. 15 to simplify the drawing. In Fig. 150 the five switch arms 99-92 controlled by each automatic tuning key I9 are re-arranged and spread out to make room for the circuit wires. Certain parts in Figs. 15 and 15a are indicated by the sufilx letters A-E after the reference numerals to facilitate the tracing of circuits for the diiferent stations. The heavy lines I95 and I99 represent a source of direct current, which may be a battery or the houselighting ircuit. If the latter is alternating current, a rectifier I91 is inserted between the connecting plug I99 and the direct current mains I99-I99, which also supply the requisite power to the radio receiver. As a starting point for the tracing of circuits, I have assumed that the conductor I99 is the positive main.

In Fig. 15, two branch conductors I99 and I99 lead from the feed mains I99 and I99. The red signal lamps 29 of the control units are connected in parallel to conductors I99 and I99. Wires III, I92 and I99 lead from conductor I99 to one side of the signal lamps 29 in control units QI. Q-II and Q-III, respectively. The other side of each lamp is connected by wire I99 to one of the associated switch contacts I99. The other switch contact I99 in each unit is connected to conductor I99, these last-named connections being indicated by wires I99, I99 and I91 for the first three units. When the key-locking slide 92 of a unit is actuated, the circuit of the associated signal lamp 29 is closed through switch 99-I99. A resistance I99 may be inserted in conductor I99 to cut down the voltage through lamps 29 to the required amount. The switch arms 99 and H in each control unit are connected to a common conductor, which is marked I99 in unit QI, 299 in unit Q-II and 29I in unit Q11I. These three conductors are joined in parallel to the positive branch line I99.

The switch arms 99 associated with keys A- E of unit Q-I are connected by wires 292-299 to conductors 291-2I I, respectively. The switch arms 99 for keys I9A-I9E of unit QII are connected to conductors 291-2I I by wires 2 I2-2 I 9, respectively, and the switch arms 99 of keys I9A-I 9E in unit Q11I are connected to conductors 291-2II by wires 2I1-22I respectively. The individual station-indicating lamps I99 in unit Q-I for stations A-E are connected at one side by wires 222-229 to conductors 221-29I respectively. Similarly, the station-indicating lamps I99 of units Q-II and Q-III for stations A-E are connected at one side to conductors 221-29I by ten wires marked consecutively 292-29I. In other words, corresponding lamps I99 in the different units are connected in parallel to the same conductor. The station lamps I99 are connected at the other side to a common conductor 292 through parallel branches 299, 299, and 299 for the first three units represented in Fig. 150. The station lamps for additionalunits would be connected in the same way. It will be noticed 5 that conductors I99, 299, and NI are connected in parallel between conductors I99 and 292.

There are five conductors marked 299-299 (near the top of Fig. 15) to which the five station selecting keys I9A-I9E of unit Q-I are connected m by wires 29I-299 respectively. The selecting keys I9A-I9E of unit Q-II are connected to conductors 299-299 by wires 299-299, respectively, and the selecting keys I9A-I9E of unit Q-III are connected to conductors 299-299 by wires 29I-299 respectively. It is seen from this that corresponding keys I9 of the various control units are connected in parallel to one of the conductors 299-299. The other five automatic tuning keys for stations F-K would be similarly connected to five other conductors. The switch arms 92 of unit Q--I are connected in parallel to a wire 299 which is connected to a conductor 291. The switch arms 92 of control unit Q-II are joined in parallel by a wire 299 connected to a con- 2 ductor 299. In unit Q-IH, the switch arms 92 are connected in parallel by a wire 219 to a conductor 21I. One end of each conductor 291, 299, and 2" is connected to the associated tuning key I9, and the other end of the conductor go is connected to one side of the electromagnetic winding 99 which controls the key-locking slide 92. In Fig. a thewinding 99 in each unit is indicated diagrammatically as two coils connected in series, but for convenience we shall consider them as a single coil or winding. The conductor 212 (near the bottom of Fig. 15) is connected in parallel to the other side of coils 99 by wires 219, 219, and 215, respectively. A wire 219 (near the middle of Fig. 156) is Joined 40 to conductors 291, 299, and 2H, to which the switch contacts II9 are connected. The switch arms II9 carried by the slides 92 are connected in parallel to conductor 292.

The common contact bar 99 mounted In each a control box below (or behind) the movable switch arms 92 is represented in Fig l5a'as a conductor connected at one end to conductor 292 and at the other end to conductor 211. In other words, the common contact bars 99 of the variw ous control units are connected in parallel between conductors 292- and 211. Conductor 211 also acts asa common connection for branch wires 219, 219, and 299 that lead to one side of the associated releasing coils 19. The other side 5 of each coil 19 is connected to the stationary contact 92 in the control unit. The switch arms 91 of the control units are connected in parallel to conductor 211 by wires 29I, 292 and 299, which may in practice be merely continuations of wires w 219, 219, and 299 respectively. The stationary contacts 12 of the control units are connected in parallel by wires 295, 299, and 291 to a conductor 299 which leads to one side of motor I99. The other side of the motor is connected to conductor 299 which leads to the power main I99. The switch arms 19 (near the bottom of Fig. 150) are connected in parallel to a common conductor 299 which is connected to power main I99.

The switch arms I2I in the radio receiver (near the top of Fig. 15) are connected in parallel to conductor 299 by branch wires 299-299. The switch arms I29 are connected to conductors 291-2II by wires 295-299, respectively. The switch arms I29 are connected in parallel to con- 7 the projection I34 on arm I2I.

ductor m by wires soc-m respectively. The

pairs of switch arms I28-I28 are connected in series to a conductor 388, which is connected at its ends to conductors 212 and 288. The stationary switch contacts I22 are connected to conductors 221-23I by wires 888-3I8 respectively. The switch-controlling coils I38 are connected at one side to the individual conductors 248-288 by wires 3II-8I5 respectively. The other side of each coil I35 is connected to a common return conductor 3I8, which leads to the power main I88.

Let us suppose that we want to bring in station C from unit Q-II. when the tuning key I40 is pushed in, the circuit of coil I380 is closed through the following connections: Starting at the main service lead I85, we go through conductors I88 and 288, across switch contacts 38-38 closed by key I40, wires 288 and 248, wire 3I3, coil I350, and through wire 3I8 to the return main I88. The energized coil I380 pulls down 'the free end of the adjacent spring arm I2I (see Fig. 10), but without affecting the associated switch assembly. The purpose of energizing coil I350 is to place the spring arm I2I in condition to snap into operative position when the notch I28 of disk II80 registers with The operation of key I40 closes the circuit of electric motor I43 as follows: Main lead I88, conductors I88 and 288, switch contacts 48-4I closed by key I40, through wire 2I4 to wire 288, through wire 281, closed switch I23--I24, conductor 284, through the windings of motor I43, and through conductor 288 to the return main I88. The motor now rotates the tuning shaft I I1 until the notch I28 of disk II80 comes into alignment with projection I34 on the tensioned spring arm I2I, whereupon the associated switch assembly moves into the position shown in Fig. 11. That is to say, the switch I2II22 is closed and switches I23-I24 and I28-I28 are opened. The opening of switch I23I24 breaks the motor circuit and instantly stops rotation of the tuning shaft, so that the selected station 0 remains in tune.

When the tuning key I40-oi unit Q-II is pushed in, the slidable plates 82 in all control units are instantly moved to key-locking position by the energization of electromagnets 88. For the magnet coil 58 of unit 62-11, the circuit is closed as follows when key I40 is-operated: Service lead I85, conductors I88 and 288, wire 242,

common contact bar 48 which is now engaged by the associated switch arm 42, wires 288 and 288, through coil 58, wires 214 and 212, through conductor 385 and the closed switches I28-I28 in series, and through conductor 288to the return main I86. The energized coil 58 of unit Q-II moves the slide 52 to key-locking position, as previously explained, and at the same time closes the switch contacts II4-II8. The closing of this switch completes the circuits through coils 58 of all other control units. From conductor 242 the currentnow passes through closed switch II4-II5 of unit QII to conductor 218, which forms a common connection between conductors 261, 288 and 2H. Therefore, current flows through conductor 281, coil 88 of unit Q-I, wire 213, common conductor 212, and through the return conductor 885 as above described. Also, from conductor 218 the circuit of coil 88 in unit QIII is completed through wires 21I, 218, 212, and 385. The operation of slides 82 to locking position automatically closes the associated 88-488, so that the red signal lamps 28 are lighted on all panels as a warning that somebody is tuning the radio receiver.

when station 0 is in tune, that fact is automatically indicated on every panel by the 1ight- 5 ingof lamp I880. As heretofore mentioned, when the projection I84 of the tensioned spring arm I2I snaps into notch I28 of the associated disk II80, switch I2II22 is (closed, and this closes the-circuit of lamp I880 of unit Q-II 1 through the following connections: From main line I88 through conductors I88, 288, 242, and 244, through lamp I880 and wire 234 to conductor 228, through wire 888 to closed switch I2II22, wire 282, and through conductor 288 15 to the return lead I88. If desired, a'resistance 8I1 may be inserted in conductor 288 toreduce the voltage for lamps I88. The corresponding station-indicating lamps I880 on all the other panels are automatically lighted when the se- 20 lected station is in tune. The circuit of lamp I 880 in unit Q-I isclosed through conductors I88, I88, 242 and 243, through lamp I880 and wire 224 to common conductor 228, and from there through the closed switch I2II22 of disk 25 I I to the return main I88 as above described. The circuit of lamp I880 in unit Q-III is closed through conductors I88,'28 I, 242, and 248, through lamp I880, wire 238, common conductor'228, and from there as previously described for lamp I880 0 in unit Q-II. The lighting of lamps I880 on all the panels informs the occupants of the rooms which particular station is in tune, so that anyone may receive the broadcast program through the loudspeaker S by simply closing the main 35 are de-energi zed, and this happens as soon as 45 the selected station is in tune. The actuated slides 82, however, do not return to normal position because they are held in key-locking position by the pins or projections 15 of electromagnets 13. Consequently, to release the slides 82 50 it is necessary to energize one of the coils 13 by depressing the associated release key I 8. Let us assume that the operator of unit Q-I, whose tuning keys were automatically locked on the operation of key I40 in unit Q-gII, wants to 5 bring in a station of his own selection. The first thing he does is to operate key I8 which closes the circuit of coil 13 through the following connections: power main I85, conductors I88 and I88 to common conductor 242, wires 48 and 218, go coil 13, closed contacts 82--18, and through conductor 288 to the return lead I88.. When the energized coil 13 pulls the locking pin 15 away from slide 52, the latter is instantly restored to normal unlocking position by springs 51. The 5 tuning keys I4 and I8 on panel QI are now free for operation. The actuation of any release key I8 energizes the coils 58 of all control units through a common connection 3| 8 between the switch contacts 82. In the example above given, 70 i where the operator oi unit Q-I pushes the recoil i35Cisde-energisedtorelea'sethespring arm Hi. The return or spring arm |2| tonormal position opens switch III-I22 and closes the switches |23-|24 and |2ll23.

Ithasbeenassumedthateach remotecorrtrol unit has ten keys l4 for automatically selecting ten different stations. This number of stations is more than will probably be used in any locality. Under the present system of sending all the important broadcast programs through a network of stations from coast to coast, a person will seldom need more than live or six stations for all the worth-while programs that may be received. It may, however, happen that a person wants a station not represented by the automatic tuning keys l4. Or, not knowing which stations are broadcasting, a person might find it too bothersome to operate each key I4 until he gets what he wants. To enable the operator to dial the receiver for a suitable program, is the function of the dialing key l3, which operates the tuning shaft of the receiver from one end of the dial to the other until the key is released. Turning to the circuit diagrams of Figs. l5l5a, if the dialing key l3 of unit QI is pushed in, the circuit of motor 3 is closed as follows: From the common conductor 242, which-is connected to the branch conductor |33, we go through wire 43 to conductor 211, through closed switch 3112, wire 235, conductor 234, through windings of motor I43, and through connection 233 to the return lead I33. The motor circuit is similarly closed when any one of,the other dialing keys i3 is pushed in. The motor |43 rotates the tuningshait H1 at the required low speed, so that the operator can hear the kind of program that is I coming across as each station reaches tuning position. when the operator gets the desired broadcast, he simply releases key l3 and the motor stops, leaving the desired station in tune. The electromagnets l 35 remain de-energized during this dialing operation, so that the disks 3 on shaft H! are free to rotate without interference by the asociated spring arms |2|.

when the dialing key N of unit QI is pushed in, the switch contacts 66 and 61 are closed, whereby the coils 59 of all control units are energized to move the slides 52 to key-locking position and at the same time light the red signal lamps 20, as heretofore explained. It is necessary that the dialing keys |8 should have suflicient movement to open the motor switch 61--12 when the actuated key is released. This required movement of key i3 is made possible by the wide slot '65, as previously-described in connection with Figs. 8 and 8a. When the slides 52 in the remote control units are moved to locking position, they also lock the dialing keys |3 in normal position, because the arm or extension 64 of each slide enters the slot 155 of the associated key l3. This was fully explained in the description of Figs. 8 and 8a. However, when a dialing key i3 is pushed in, the extension 34 of slide 52 enters the wide slot 65 of the key, so that the latter is free to return part way to normal position, whereby the motor switch 61-12 is opened to stop the tuning shaft instantly upon release of the key. The dialing keys |3 of all the other panels remain locked against operation until a releasing key I3 is pushed in.

In the wiring diagram of Fig. 16, the two pairs of switch contacts 93-44 and 35-33 operated by 323, which lead from the service mains I33 and I3! respectively. The conductor 323 contains a coil 32| of an electromagnetic relay 322, and a resistance 323 may be included to cut down the voltage through the coil. An armature 324 is 5 pivoted at 323 to the magnetic frame of the relay, and the free end of the armature is in operative relation to a movable switch arm 323, which may be a spring blade mounted at one end. A wire 321 connects the switch arm 323 to service main I33, and a contact 323 associated with arm 323 is connected with conductor 3|3 by a wire 323. The normal set or tension of spring arm 326 holds it away from contact 323. Asmall contracting coil spring 333 normally holds the pivoted armature 324 against a fixed stop 33 When the coil 32| is energized by the closing of any one of theswitches 33-34, the armature 324 is rocked toward the magnetic frame of the relay and forces the switch arm 323 against the associated go contact 323. This closes the power circuit |85 I33 for radio receiver R and all apparatus connected therewith. In other words, the parts 323-323 constitute a main power switch adapted to be controlled from any unit Q by means of the movable finger. piece It. The main switch indicated diagrammatically by the movable member 332 is embodied in the cabinet of receiver R and may be assumed to be operated by knob 333 on the front panel of the cabinet. Since the two main switches 326--323 and 332 are in parallel, they are independently operable to open and close the power circuit ||36. The relay coil 32| operates at such low voltage that no arcing occurs at the switch contacts 3394. In Fig. It the a main switch 323-328 is shown closed, because the relay coil 32| is energized through the closing of switch 33-94 on panel Q-I.

I mentioned in connection with Fig. 1 that the signal lamp 2| in each control unit is automatio cally lighted when the main switch It is thrown on. This will be clear from Fig. 16 where it is seen that the circuit of relay coil 32| is closed through any one of the signal lamps 2|, which are connected in parallel between conductors 3|9 and 323. One ternu'nai of each lamp is connected to the associated switch arm 93 by a wire 334. The other terminal of each lamp is connected by a wire 335 to conductor 3|9. It may be advisable to shunt a resistance 336 across each lamp 2| to insure the operation of relay coil 32| even if a lamp should happen to burn out. As stated before, the lamps 2| may shine through a bright green lens to indicate vividly that the radio receiver R and loudspeakers S are connected to the power circuit. The loudspeakers S in Fig. 16 are supposed to be of the moving coil type and the vibratory speech coils are indicated diagrammatically by the dotted circles 331. The speech coil 331 of loudspeaker S of control unit QI is connected by conductors 338 to a secondary coil 333. Similarly, the speech coils 331 of the other two loudspeakers S are connected by conductors 343 and 3 to secondary coils 342 and 343 respectively. The three secondary coils 333, 342, and 343 are inductively related to a common primary coil 344 of an output transformer indicated as a whole by 345. It is assumed that the primary coil 344 is properly connected to the output terminals of radio receiver 10 R. The circuit of each loudspeaker coil 331 contains the rheostat ||l|||2, which is here in series with the coil, but it might also be connected in shunt thereto. By adjusting the rheostat arm III, the resistance of the speech circuit is varied 13 and the volume of reproduction is regulated accordingly.

Still referring to Fig. 16, the field coils of loudspeakers B are connected in parallel to a. pair of leads 346 and 341, which are connected to the power supply line to iurnish a substantially constant current oi the required voltage, as will be understood without further explanation. The terminals 343 of loudspeakers S are connected in parallel to conductor 346, and the other terminals 343 are connected in parallel to switch arms 35 by wires 350. The switch contacts 36 are connected in parallel to conductor 34'! by wires 35L When the finger piece N on the.control panel is in oti'f position, the associated switch 35-36 is open, so that no current-passes through the field coil of the connected loudspeaker. The closing of the main switch 326-326 is always accompanied by the closing of the associated loudspeaker switch 35-36, so that no separate operation is required for placing the loudspeaker in operative condition. When electric impulses pass through the primary output coil 344, similar impulses are induced simultaneously in the secondary coils 333, 342, and 343. However, the energization of the vibratory speech coils 331 does not render the loudspeakers operative unless the main switch l6 of a unit is closed to energize the field coil of the connected loudspeaker. Instead of having a single primary coil 344 for all secondary coils, it is evident that each secondary coil may have its own primary coil. Although Fig. 16 shows the circuit connections for three loudspeakers only, it will be readily understood how additional loudspeakers can be connected to their respective control panels. The relative turns in primary coil or coils 344 and the associated secondary coils can readily be determined by the builder to produce the best results with any particular type of loudspeaker. Some loudspeakers are capable of carrying more power than others. If the radio receive R has a loudspeaker of its own, its volume may be controlled in the recalled that in the system of Figs. 15-150, the

operation of any dialing key. l8 automatically energizes the coils 53 of all units to move the slides 52 to key-locking position. In the modification of Fig. 22 the circuit arrangements are such that, when the dialing key l3 of a unit is actuated, the slide 52 of that unit is not moved to locking position, but the slides of all the other units are actuated to look all the tuning keys. Fig. 22 shows'only the circuit connections below the common conductor 242, because everything above that conductor is supposed to be the same as in Fig. 15a. To avoid needless repetition of description, I have indicated similar parts in Figs. 15a and 22 by the same reference-numerals. In Fig. 22 each dialing key I6 operates four switch arms 353, 354, 355, and 356. The switch arms 354 and 356 are mechanically connected by an insulating pin 35! which may be secured to position upon release.

verse partitions I32. When the key I 3 is pushed 5 in, the switch arm 353 is first moved into contact with arm 354, which first moves the switch arm 356 away from contact 353 and then engages the adJacent arm 355. The point to remember is that the switch 356-353 is opened before the 10 switch 345-355 is closed. The reason for this will presently be explained. A fixed stop 356 on thebottom 22 of the control box engages the arm 356 for limiting the inward movement of key I3. 7 l5 Reierring to Fig. 22, the switch contacts 353 are connected in parallel to conductor 264 by wires 363, and the switch arms 354 are connected in parallel to conductor 2'" by wires 361. The switch arms 355 are connected in par- 20 allel to a common conductor 362 by wires 363 to which the switch arms 356 are also connected. Let us say that the dialing key l3 of control unit Q-I has been pushed in. The circuit through electric motor i 43 (see Fig. 15) is closed through 25 wire 46 (which is connected to service lead I of Fig. 15, as previously explained) to connecting point 364, wire 36l, across the closed switch contacts 354-353, wire 363, and through conductor 284 which is connected to one terminal of the 30 motor windings. The closing of switch 354-355 on the operation of key l3 closes the circuits of coils 53 in units Q-II and Q-III, but not the circuit 01' coil 53 in unit Q-I, to which the actuated key l3 belongs. 35

coils 53 in units Q-II and Q-III, because the 45- circuits of those coils are completed through the following connections: For coil 53 in unit Q-II, we follow the circuit from the common conductor 242 through wire 43 in unit Q-I, conductor 2" to point 364, wire 36i, through closed switch 50 354-355, wires 365 and 366, through the closed switch 356-353 of unit Q-II, wire 263, through coil 53 of that unit, and back to the return lead as previously explained in connection with Figs. 15-1511. For coil 53 of unit Q-III, the cir- 5 cuit is closed through conductor 365, wire 361, through the closed switch 356-353 of the'unit, wire 2', through coil 53, and so on as before. When the dialing key l8 of unit Q-II is operated, the coils 53 of the other units are en- 60 ergized to actuate the key-locking slides 52, but the coil 53 of unit 62-11 is not energized so that the actuated key is free to return to normal Since the modification in Fig. 22 requires more switches for the dialing 65 keys l3, it is perhaps not so desirable as the dialing circuits of Figs. 15-15a, but it is nevertheless a practical construction and may be preferred by some radio engineers.

In Fig. 19 there is a box or cabinet indicated 70 as a whole by 363, which contains not only the remote control mechanism, but also the loudspeaker S. This cabinet constitutes a combined loudspeaker and remote control device as a unitary structure adapted to be placed anywhere 75 

